This disclosure relates to medical devices and, more particularly, stimulators that may deliver electrical stimulation to one or more electrodes.
Electrical stimulators may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, epilepsy, urinary or fecal incontinence, sexual dysfunction, obesity, or gastro paresis, and may also be used to deliver electrical stimulation to the brain, such as in deep-brain stimulation. An electrical stimulator may deliver electrical stimulation therapy via leads that include electrodes located proximate to the spinal cord, pelvic nerves, stomach, peripheral nerves, or within the brain of a patient. In many cases, the stimulator and/or the electrodes are implanted.
A clinician selects values for a number of programmable parameters in order to define the electrical stimulation therapy to be delivered to a patient. For example, the clinician may selects an amplitude, which may be a current or voltage amplitude, and, when electrical stimulation is delivered in the form of pulses, a pulse width for a stimulation waveform to be delivered to the patient, as well as a rate at which the pulses are to be delivered to the patient. The clinician may also select particular electrodes within an electrode set to be used as an electrode combination to deliver the electrical stimulation, as well as the polarities of the selected electrodes. A set of parameter values may be referred to as a program in the sense that they drive the electrical stimulation therapy to be delivered to the patient.
In some cases, electrical stimulation is delivered via electrodes carried by one, two or more implantable leads, each of which may include multiple electrodes. Electrical stimulation may be delivered via various combinations of electrodes, including electrodes on a single lead, or electrodes on different leads. For example, one program may specify a combination of electrodes located relatively proximally on one or more leads while another program may specify a combination of electrodes located more distally on the one or more leads. In addition, some programs may include greater or lesser numbers of electrodes, greater or lesser distances between electrodes, or varied positions of cathodes and anodes. In this manner, electrical stimulation can be shaped and targeted relative to nerves, muscle or other tissue or anatomical structures to enhance therapeutic efficacy.
In some cases, an electrical stimulator may include multiple electrical sources. For example, the electrical stimulator may include multiple current sources that may each deliver current having a positive polarity (positive current sources), as well as multiple current sources that may each deliver current having a negative polarity (negative current sources). Each electrode coupled to the stimulator may be directly connected to one positive current source and one negative current source. In such fashion, the electrode may be programmed as either a cathode (when its connected negative current source is activated) or as an anode (when its connected positive current source is activated).
Some electrical stimulators have included fewer electrical sources than the number of available electrodes. Such electrical stimulators have included a multiplexer or other switching unit to connect the electrical sources to a greater number of electrodes. In such electrical stimulators, the electrical sources are not directly coupled to any electrode. In other words, in such electrical stimulators, the switching unit is always used to couple a selected electrode to an electrical source.